How do I solve an algebraic expression when the unknown is on both sides of the equals sign?

the basic idea is to get everything with the unknown (let's assume this is x) on one side of the equals and everything else on the other side. To do this we use the 'inverse idea' to move our items onto different sides of the equals sign. For example, if we have a 2x on one side, we will move this to the other side by doing -2x. You should end up with something that has x's on one side and a number on the other.

you can then solve this as usual - dividing through by the number in front of the x.